WO2015133452A1

WO2015133452A1 - Rigid core for tire formation and tire production method using same

Info

Publication number: WO2015133452A1
Application number: PCT/JP2015/056151
Authority: WO
Inventors: 圭小原
Original assignee: 住友ゴム工業株式会社
Priority date: 2014-03-07
Filing date: 2015-03-03
Publication date: 2015-09-11
Also published as: CN106029321B; EP3115167A4; US20170057188A1; CN106029321A; US9731463B2; EP3115167A1; EP3115167B1; JP6212413B2; JP2015168173A

Abstract

Provided is a rigid core for tire formation that limits the biting of rubber between core segments in a core production method while minimizing the occurrence of unevenness in the radial direction between core segments that is caused by thermal expansion. A core main body (2) is divided into: a first core segment (5A) in which both circumferential end surfaces (5As) are inclined radially inward in a direction in which the circumferential width increases; a second core segment (5B) that is arranged in an alternating manner with the core segment (5A) and in which both circumferential end surfaces (5Bs) are inclined radially inward in a direction in which the circumferential width decreases; and a butting member (6) that is arranged between the first core segment (5A) and the second core segment (5B). The Young's modulus (Ea) of the butting member (6) is smaller than the Young's modulus (Eb) of the first and second core segments (5A, 5B).

Description

Rigid core for forming tire and method of manufacturing tire using the same

In the core method, the present invention provides a rigid core for forming a tire capable of suppressing the occurrence of a radial step between core segments caused by thermal expansion while suppressing rubber biting between the core segments, and The present invention relates to a tire manufacturing method using the same.

In recent years, a method for manufacturing a tire using a rigid core (hereinafter sometimes referred to as “core method”) has been proposed in order to increase the accuracy of tire formation (see, for example, Patent Documents 1 and 2). This rigid core has a core body having an outer shape that matches the shape of the tire lumen surface of the vulcanized tire, and a tire component is sequentially pasted on the core body to form a raw tire. Is done. The raw tire is inserted into the vulcanization mold together with the rigid core, so that the raw tire is vulcanized and molded between the inner core body and the outer vulcanization mold. Is done.

As shown in FIG. 8A, in the core method, the core body a is divided into a plurality of core segments c in the circumferential direction in order to take out the core body a from the vulcanized tire. Has been.

The core segment c includes a first core segment c1 having a small circumferential width with both circumferential end faces as the first mating face sc1, and a circumferential direction with the circumferential end faces as the second mating face sc2. The second core segment c2 has a large width. The core body a is formed in an annular shape by abutting the first and second mating surfaces sc1 and sc2 adjacent in the circumferential direction.

The first mating surface sc1 is formed as an outer inclined surface that is inclined in the direction in which the circumferential width increases inward in the radial direction, and the second mating surface sc2 is in the circumferential width inward in the radial direction. It is formed as an inner inclined surface that is inclined in a direction in which the angle decreases. Accordingly, the first core segment c1 can be moved and removed one by one radially inward. That is, the core body a can be disassembled and taken out from the tire.

However, in the core body a, the temperature rises from a normal temperature state (about 15 to 50 ° C.) at the time of raw tire formation to a high temperature state (100 ° C. or more) at the time of vulcanization molding. Therefore, during vulcanization molding, a pressing pressure is generated between the core segments c1 and c2 adjacent in the circumferential direction due to thermal expansion. At this time, as shown in FIG. 8B, the first core segment c1 having the mating surface sc1 as the outer inclined surface is pushed radially inward, and the mating surface sc2 is the second inner surface as the inner inclined surface. The core segment c2 is pushed outward in the radial direction. As a result, a step d in the radial direction is generated between the outer peripheral surfaces of the first and second core segments c1 and c2, and there is a problem that the uniformity of the tire is lowered.

In order to reduce the level difference d, it is proposed to reduce the pressing force at the time of vulcanization molding by increasing the gap amount between the mating surfaces sc1 and sc2 at room temperature. In this case, however, the rubber flows into the gap during the vulcanization and causes rubber biting, resulting in a decrease in tire quality.

JP 2011-161896 A JP 2011-167799 A

The present invention provides a rigid core for forming a tire that can suppress the occurrence of a step in the radial direction between the first and second core segments while suppressing rubber biting, and can improve the uniformity of the tire. It is an object of the present invention to provide a method for manufacturing the tire used.

The present invention includes an annular core body having an outer surface having a tire molding surface for forming a green tire, and the green tire and the core body are inserted into the vulcanization mold together with the green tire. A rigid core for vulcanizing the green tire with
The core body includes a plurality of first core segments whose both end faces in the circumferential direction are inclined in a direction in which the circumferential width increases toward the inner side in the radial direction, and both end faces in the circumferential direction are directed toward the inner side in the radial direction. A second core segment that is inclined in a direction in which the width of the direction is reduced and is alternately arranged in the circumferential direction with the first core segment, and a butt disposed between the first and second core segments Divided into parts,
The abutting member is fixed to the circumferential end surface of one of the adjacent first and second core segments, and
The butting member is characterized in that the Young's modulus Ea is smaller than the Young's modulus Eb of the first and second core segments.

In the present invention, as described above, a butt member is interposed between the first and second core segments. The Young's modulus Ea of the abutting member is set to be smaller than the Young's modulus Eb of the first and second core segments. Therefore, the pressing force between the core segments generated by thermal expansion during vulcanization can be absorbed and relaxed by compressing and deforming the butt member. Therefore, the radial step generated between the first and second core segments can be reduced, and the tire uniformity can be improved.

The butting member is fixed to one core segment of the first and second core segments. Therefore, the disassembly workability of the core main body can be maintained at the same level as before. Further, since it is not necessary to widen the gap between the butting member and the other core segment, the occurrence of rubber biting can be suppressed.

It is sectional drawing which shows the vulcanization | cure process in the manufacturing method of the tire of this invention. (A), (B) is the perspective view of a core main body, and the partial side view which expanded the part. (A), (B) is the perspective view and side view which show the fixed state of a butting member and one core segment. It is a side view explaining decomposition | disassembly of a core main body. It is a distribution map of the pressing force in the circumferential direction end surface of the core segment. It is sectional drawing explaining the convex-shaped trace which originates in a butting member and generate | occur | produces on the inner surface of a vulcanized tire. (A) is a side view which shows the other example of fixation of a butting member, (B) is a side view which shows the other example of a core segment. (A) is a side view of a conventional core body, and (B) is an enlarged side view showing a state of occurrence of a step.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the rigid core 1 for forming a tire according to the present embodiment includes an annular core body 2 having a tire molding surface S on the outer surface. On the tire molding surface S, tire constituent members such as a carcass ply, a belt ply, a sidewall rubber, and a tread rubber are sequentially attached to form a green tire T having substantially the same shape as the finished tire. Further, by putting the raw tire T together with the rigid core 1 into the vulcanizing mold B, the raw tire T is interposed between the core body 2 which is the inner mold and the vulcanizing mold B which is the outer mold. Is vulcanized. The tire molding surface S is formed in substantially the same shape as the inner surface shape of the finished tire.

The rigid core 1 includes an annular core body 2 and a cylindrical core 3 inserted into the center hole 2H. Other than the core body 2, a conventional well-known structure can be adopted. Therefore, in this specification, only the said core main body 2 is demonstrated below.

The core body 2 of the present example has a hollow shape including a lumen portion 4 extending continuously in the circumferential direction, for example, and the raw tire T is heated inside the lumen portion 4. A heating means (not shown) such as an electric heater is arranged.

As shown in FIGS. 2A and 2B, the core body 2 is disposed between a plurality of first and

second core segments

5A and 5B that are alternately arranged in the circumferential direction. The butt member 6 is divided. In the first core segment 5A, both circumferential end surfaces 5As are inclined in a direction in which the circumferential width increases inward in the radial direction (sometimes referred to as “outside inclination”). On the other hand, in the second core segment 5B, the circumferential end faces 5Bs are inclined in the direction in which the circumferential width decreases toward the inner side in the radial direction (sometimes referred to as “inner inclination”). The butting member 6 has a plate shape in which both circumferential end surfaces 6s are parallel to each other, that is, the circumferential thickness t is substantially constant.

The abutting member 6 is fixed to a circumferential end surface of one core segment of the adjacent first and

second core segments

5A and 5B. In this example, as shown in FIGS. 3A and 3B, each butting member 6 is fixed to the circumferential end surface 5As of the first core segment 5A in a replaceable manner using, for example, screws 8 or the like. That is, in this example, the first core segment 5 </ b> A is formed as a composite core segment 9 that is integrally joined to the

butting members

6 and 6.

Therefore, as shown in FIG. 4, in this example, the core body 2 is annularly formed by abutting the circumferential end surface 9s of the composite core segment 9 and the circumferential end surface 5Bs of the second core segment 5B. Can be combined. Further, the combined core body 2 can move radially inward from the composite core segment 9 in order. That is, after vulcanization molding, the composite core segments 9 can be taken out one by one from the bead holes of the vulcanized tire in order. The core 3 prevents the

core segments

5A and 5B from moving inward in the radial direction, and holds the combined core body 2 in an annular shape.

Next, the Young's modulus Ea of the butting member 6 is set to be smaller than the Young's modulus Eb of the first and

second core segments

5A, 5B.

Here, the radial step d (shown in FIG. 8B) between the first and

second core segments

5A and 5B due to thermal expansion occurs as follows. Due to the heat of vulcanization at the time of vulcanization molding, the core body 2 undergoes thermal expansion not only in the radial direction but also in the circumferential direction. Due to the thermal expansion in the circumferential direction, a circumferential pressing force acts on the circumferential end faces 5As and 5Bs of the first and

second core segments

5A and 5B. At this time, the circumferential end faces 5As and 5Bs are inclined outward and inward, respectively. As a result, the first core segment 5A inclined outward is pushed out in the radial direction and displaced, and the second core segment 5B inclined inward is pushed out in the radial direction and displaced. The step d is caused by this positional shift. The step d becomes larger as the circumferential pressing force is higher.

In the present invention, a butting member 6 having a small Young's modulus Ea is interposed between the first and

second core segments

5A and 5B. Accordingly, the pressing force applied to the

core segments

5A and 5B generated by the thermal expansion in the circumferential direction can be absorbed and relaxed by the butt member 6 being compressed and deformed.

On the other hand, since the core body 2 is formed in substantially the same shape as the inner surface shape of the finished tire, it thermally expands in a complicated manner. That is, when the

core segments

5A and 5B are produced, even when the circumferential end surfaces 5As and 5Bs are processed into a flat surface at room temperature, the circumferential end surfaces 5As and 5Bs are deformed into a curved surface in the vulcanization temperature state. As a result, the pressure distribution is non-uniform. FIG. 5 shows an example of the distribution of the pressing force when the butting member 6 is not provided. The figure shows an aluminum core body 2 (lumen portion 4) in which the circumferential end faces 5As and 5Bs are flat and the distance between the end faces 5As and 5Bs is 0.07 mm (constant) in a normal temperature state (20 ° C.). Is a distribution of the pressing pressure between the end faces 5As and 5Bs when the temperature is raised to the vulcanization temperature (150 ° C.). As the color becomes darker, the pressure increases.

As described above, since the distribution of the pressing force is non-uniform, when the butt member 6 is interposed, the distribution of the compressive deformation is also non-uniform. Therefore, when the thickness t in the circumferential direction of the butt member 6 is too thin, the ratio of the compressive strain to the thickness t becomes excessive, and the butt member 6 tends to be damaged. From such a viewpoint, the thickness t is preferably 1.0 mm or more, and more preferably 4.0 mm or more. If the thickness t of the butting member 6 is too thick, the radially outer end surface of the butting member 6 is pressed by the pressure of the rubber G during vulcanization, as shown in FIG. It will be dented inward in the radial direction. As a result, convex marks 20 are generated on the inner surface of the vulcanized tire T, which tends to deteriorate the tire quality. From such a viewpoint, the thickness t is preferably 10.0 mm or less, and more preferably 6.0 mm or less.

The Young's modulus Ea of the butting member 6 is preferably 10% or less of the Young's modulus Eb of the first and

second core segments

5A and 5B. If the Young's modulus Ea exceeds 10% of the Young's modulus Eb, the effect of absorbing the pressing force by the butt member 6 becomes small, and the step d between the first and

second core segments

5A and 5B is reduced. It becomes difficult to suppress sufficiently.

The smaller the ratio Ea / Eb between the Young's modulus Ea and the Young's modulus Eb, the more preferable from the viewpoint of the effect of suppressing the level difference d. However, if the Young's modulus Ea itself is too small, the butt member 6 is pressed by the pressure of the rubber G during vulcanization and is recessed in a concave shape, and the convex trace 20 tends to be caused on the inner surface of the vulcanized tire T. Become. On the other hand, even if the Young's modulus Ea itself is too large, it becomes difficult to compressively deform and the effect of suppressing the level difference d decreases. From such a viewpoint, the lower limit of Young's modulus Ea is preferably 0.1 GPa or more, more preferably 0.4 GPa or more, and the upper limit is preferably 2.0 GPa or less, more preferably 1.0 GPa or less.

As a conventional core body material, for example, a lightweight metal material such as aluminum or an alloy thereof (aluminum alloy) is generally used from the viewpoint of durability, handleability, and energy efficiency. In the core body 2 of the present invention, from the same viewpoint, a lightweight metal material such as aluminum or an alloy thereof (aluminum alloy) is preferably employed as the material of the first and

second core segments

5A and 5B. sell.

On the other hand, as the butting member 6, a heat-resistant synthetic resin material is suitable, for example, silicon resin (silicon rubber), allyl resin, polyamideimide resin, fluorine resin, polyphenylene sulfide resin (PPS), polyethylene terephthalate resin. (PET). Table 1 shows an example of the Young's modulus. As shown in the table, examples of those having a Young's modulus Ea in the range of 0.1 to 2.0 GPa include fluororesins and allyl resins.

In this example, the case where the butting member 6 is fixed to the circumferential end surfaces 5As of the first core segment 5A is illustrated. However, the butting member 6 can also be fixed to the circumferential end surfaces 5Bs of the second core segment 5B. Further, as shown in FIG. 7A, the abutting member 6 is connected to the end surface 5As on the one side in the circumferential direction of the first core segment 5A (right side in the figure) and the one side in the circumferential direction of the second core segment 5A. It can also be fixed to the end face 5Bs (right side in the figure).

Further, in the core body 2, the inner cavity portion 4 is not continuous in the circumferential direction, and as shown in FIG. 7B as a representative of the first core segment 5A, In other words, the lumen 4 can be formed without opening at the circumferential end faces 5As and 5Bs and the inner circumferential surface. In this case, a heating fluid such as steam can be adopted as the heating means, and this heating fluid flows into each lumen 4.

Next, the tire manufacturing method includes a green tire forming step and a vulcanizing step. In the green tire forming step, a green tire T is formed by sequentially affixing tire components such as carcass ply, belt ply, sidewall rubber, and tread rubber on the tire molding surface S of the rigid core 1. . In the vulcanization step, the raw tire T obtained in the raw tire formation step is put into the vulcanization mold B together with the rigid core 1 as shown in FIG.

As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

In order to confirm the effect of the present invention, a core body 2 for forming a pneumatic tire having a tire size of 195 / 65R15 was prototyped with the structure shown in FIG. Then, when a pneumatic tire is formed using the core body 2, the generation state of the radial step d (shown in FIG. 8B) between the core segments 5 </ b> A and 5 </ b> B, the convex trace at the butt position 20 (shown in FIG. 6), the occurrence of rubber biting at the butting position, and maintainability were evaluated.

Aluminum (Young's modulus Ea = 71 GPa, thermal expansion coefficient = 2.38 × 10 ⁻⁵ / degree) is used as the first and

second core segments

5A, 5B. Further, as the butting member 6, a heat-resistant synthetic resin material described in Table 1 is used. The temperature of the core body 2 at the time of green tire formation is 20 ° C., and the temperature of the core body 2 at the time of vulcanization is 150 ° C. The gap between the butted surfaces at 20 ° C. is 0.15 mm. The specifications are substantially the same except for those listed in Table 2.

(1) Leveling situation:
When the core body was heated to 150 ° C., the radial step between the first and second core segments on the tire equatorial plane was measured with a dial gauge, and the measured value was evaluated by an index. The smaller the value, the smaller the step and the better.

(2) Occurrence of convex marks:
The inner surface of the tire after vulcanization molding was observed, and the product of the width and height of the convex marks at the butting position was quantified and evaluated by an index. The smaller the numerical value, the smaller the convex mark and the better. Evaluation was performed in the initial stage (first tire).

(3) Status of rubber biting:
The inner surface of the tire after vulcanization molding was observed, the amount of rubber biting at the butt position was quantified and evaluated by an index. The smaller the value, the less the rubber bite and the better. Evaluation was performed in the initial stage (first tire).

(4) Maintainability:
Using each core body, tires were formed at a pace of 150 per day for 100 days (15000). The number of exchanges due to damage of the butt member at that time was quantified and evaluated by an index. The smaller the number, the fewer the number of replacements and the better.

As shown in the table, in the examples, it can be confirmed that the occurrence of a step in the radial direction between the first and second core segments can be suppressed while suppressing the rubber biting.

DESCRIPTION OF SYMBOLS 1 Rigid core 2 Core body 5A 1st core segment 5B 2nd core segment 6 Butting member B Vulcanization mold S Tire molding surface T Raw tire

Claims

An annular core body having a tire molding surface for forming a green tire is provided on the outer surface, and the raw tire is inserted into the vulcanization mold so that the vulcanization mold and the core body A rigid core for vulcanizing the green tire,
The core body includes a plurality of first core segments whose both end faces in the circumferential direction are inclined in a direction in which the circumferential width increases toward the inner side in the radial direction, and both end faces in the circumferential direction are directed toward the inner side in the radial direction. A second core segment that is inclined in a direction in which the width of the direction is reduced and is alternately arranged in the circumferential direction with the first core segment, and a butt disposed between the first and second core segments Divided into parts,
The abutting member is fixed to the circumferential end surface of one of the adjacent first and second core segments, and
A rigid core for tire formation, wherein the butting member has a Young's modulus Ea smaller than a Young's modulus Eb of the first and second core segments.
The tire-forming rigid core according to claim 1, wherein the abutting member has a thickness t in the circumferential direction in the range of 1.0 to 10.0 mm.
3. The rigid core for forming a tire according to claim 1, wherein a Young's modulus Ea of the butting member is 10% or less of a Young's modulus Eb of the first and second core segments.
4. The rigid core for forming a tire according to claim 1, wherein the butting member has a Young's modulus Ea in a range of 0.1 to 2.0 GPa.
A green tire forming step of forming a green tire by sequentially sticking tire constituent members on the tire molding surface of the rigid core according to any one of claims 1 to 4,
A tire manufacturing method, comprising: a vulcanizing step in which a green tire obtained by the green tire forming step is placed in a vulcanizing mold together with the rigid core and vulcanized.